Astigmatic chart.



G. 0. NICHOLSON.

ASTIGMATIO CHART. APPLICATION FILED MAY 19, 1910.

Patented Jan. 2, i912.

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A TT 0R/VE Y 8 COLUMBIA PLANOGRAPH 60.. WASHINGTON, D. c.

G. 0. NICHOLSON. ASTIGMATIU CHART. APPLICATION FILED MAY 19, 1910.

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Patented Jan.2,1912.

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GEORGE OSWALD NICHOLSON, OF LONG-BEACH, CALIFORNIA.

ASTIGMATIC CHART.

Specification of Letters Patent.

Patented Jan. 2,1912.

Application filed May 19, 1910. Serial No. 562,315.

To all whom it may concern:

Be it known that I, GEORGE O. NICHOL- SON, a citizen of the UnitedStates, and a resident of Longbeach, in the county of Los Angeles andState of California, have invented a new and Improved Astigmatic Chart,of which the following is a full, clear, and exact description.

The object of the invention is to provide a new and improved astigmaticchart, arranged to enable the operator, standing a distance from thechart, to conveniently turn the astigmatic disk to any desired position,the disk having but few astigmatic lines, to insure accuratedetermination of the patients vision without danger of confusion.

For the purpose mentioned use is made of a dial arranged for attachmentto a wall or other support, and on the face of the dial is arranged arotary disk having astigmatic lines thereon, adapted to indicate on thescale of the dial, the disk being attached to a shaft journaled on thedial and carrying a double-groove pulley, over which pass cordssupporting counterbalancing weights, one of the cords being extended adistance from the chart, to permit the operator to turn the disk from aposition adjacent to the patient, thus facilitating the work.

A practical embodiment of the invention is represented in theaccompanying drawings forming a part of this specification, in whichsimilar characters of reference indicate corresponding parts in all theviews. Figure 1 is a perspective view of the chart as applied; Fig. 2 isan enlarged face view of the chart; Fig. 3 is a rear face view of thesame; Fig. 4 is a transverse section of the same; and Fig. 5 is a planview of the same.

The dial A, of sheet metal or other suitable material, is provided atthe sides with rearwardly-extending flanges A, terminating inoutwardlyextending attaching flange A provided with, openings A adaptedto engage hooks or like supports B, attached to a wall or the like, forsupporting the dial A in a vertical position, as plainly indicated inFig. 1. The face of the dial A is provided with a circular scale C,

preferably running from 1 to 12, in the same manner as the scale of awatch dial, and in front of the dial A is arranged a disk D, theperipheral surface of which extends close to the scale C, and on theface of the disk D are arranged two sets of astigmatic lines E adaptedto indicate on the marks of the scale C, at any desired point wheneverthe disk D is rotated, as hereinafter more fully explained.

The rear face of the disk D is secured on a shaft F, journaled insuitable bearings arranged on the dial A, and a brace A connects theside flanges A with each other, and on the said shaft F in the rear ofthe dial A, is secured, by a set screw G, a double-groove pulley Hengaged by the cords I and J, extending from the pulley H in oppositedirections, that is, the cord I extends downwardly and supports at itslower end a counterbalancing weight K, while the cord J extends upwardlyand passes over guide pulleys L, L attached to the ceiling or othersupport, to lead the terminal of the cord'J to a place remote from thedial A, as plainly indicated in Fig. 1. The terminal of the cord J isprovided with a counterbalancing weight N, so 1that normally the disk Dis at a standsti 1.

Now in using the chart, the operator, standing alongside of the patientwhose eyes are to be tested, can readily turn the disk D by pulling onthe cord J so as to rotate the pulley H and with it the disk D. When thedesired position is reached, the operator releases the pull on the cordJ, so that the counterbalancing Weights K and N again hold the disk inthe adjusted position. When the operator lifts the weight N, the disk isturned in an opposite direction owing to the overbalancing pull on thecord I by the weight K. Thus, from the foregoing, it will be seen thatthe operator can conveniently and accurately turn the disk D whilestanding near the patient, to bring the astigmatic lines E into thedesired position relative to the scale C. It is well known that incorrecting the eyes for an error of astigmatism, but two meridians canbe corrected, and hence by having but two sets of lines, as shown inFigs. 1 and 2, the operator can bring the said lines into the properposition without confusing the patient, and thus the operator is enabledto quickly and accurately determine the position and degree of theastigmatism.

It is understood that when the patient looks at the two sets of lines E,and the lines appear equally clear tohis vision, then the operatorrotates the disk D to another meridian, which perhaps will show that theastigmatism is at that angle, the operator then placing a cylinder inthe eyeglass frame worn by the patient for the time being, until thelines become equal in sharpness or color, and then the operator canrotate the disk D to all the different meridians to corroborate thework.

The astigmatic chart shown and described,-is very simple and durable inconstruction, and can be readily manipulated by the operator standing ata remote place from the chart.

In the ordinary charts as now generally used, a good many lines are usedand hence the patient is liable to become confused on comparing one linewith another, while in the present invention only two sets of lines areused at a time, and comparison as to blackness or clearness of the linesis easy and the information obtained from the pa tient is reliable. Thechart can be rotated at will to all the different points of the dial,and as there are only two meridian lines to consider at a time, theentire circle is withinrange of the lines at all meridians, and thefaulty meridian is readily discovered.

Having thus described my invention, I claim as new and desire to secureby Letters Patent:

An astigmatic chart, comprising a stationary dial having at its sidesrearwa'rdly disk disposed in front of said extending side flanges bentoutwardly and provided with openings for receiving support-s in order tosustain said dial in a vertical plane, a brace extending across from oneof said flanges to the other, said brace being spaced from said dial andparallel to the same, said dial being provided on its face with anannular scale, an astigmatic dial and provided with meridian lines forregistering with said scale, said meridian lines being few in number andextending in two directions relatively to said disk, a shaft carr ingsaid disk and journaled at one of its ends in said dial and at its otherend in said brace, a pulley mounted upon said shaft and provided with aplurality of grooves lying in parallel planes, said pulley beingdisposed between said dial and said brace, cords engaging said pulleyand disposed within said grooves, said cords extending in oppositedirections from said pulley, counterbalancing weights located upon theends of said cords, and guides for one of said cords to support the sameto a place remote from said dial and said disk.

In testimony whereof I have signed my' name to this specification in thepresence of two subscribing witnesses.

I GEORGE OSWALD NICHOLSON.

\Vitnesses HARLEY E. SMITH,

C. W. SHELBY.

Copies of this patentmay be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. C.

